Was introduced to this concept of "future letters" by a teacher during an ethics class. We all had to write a letter and the teacher would give it back to us at the end of the year.
I then started to use this service occasionally and reading the letters after one year was always very interesting. I must have skipped some years since I can't remember receiving a letter every year since school. But I want to start again!
The most interesting was to see which problems I was dealing with at the time (and how insignificant they turned out to be, lol), what my goals and dreams were, which goals I achieved or made progress on and which I don't even care about anymore.